Method and arrangement for continuous calibration of a wind direction measurement

Abstract

A method for calibrating a wind direction measurement for a wind turbine is provided. The method including: measuring plural samples of a relative wind direction representing a difference angle between a real wind direction and an orientation of a measurement equipment, in particular a direction orthogonal to a rotor blade plane, to obtain plural measured relative wind directions; deriving a measured relative wind direction change based on the measured relative wind directions; measuring plural samples of a performance parameter indicating a performance of the wind turbine; deriving a performance change based on the plural samples of the performance parameter; determining a correlation value between the measured relative wind direction change and the performance change; measuring further plural samples of the relative wind direction; and correcting the further measured relative wind directions based on the correlation value, to obtain corrected further measured relative wind directions.

The invention claimed is: 
     
       1. A method for performing a wind direction measurement for a wind turbine, the method comprising:
 measuring plural samples of a relative wind direction representing a difference angle between a real wind direction and an orientation of a measurement equipment, to obtain plural measured relative wind directions, wherein the orientation is a direction orthogonal to a rotor blade plane; 
 deriving a measured relative wind direction change based on the measured relative wind directions; 
 measuring plural samples of a performance parameter indicating a performance of the wind turbine; 
 deriving a performance change based on the plural samples of the performance parameter; 
 determining a correlation value between the measured relative wind direction change and the performance change including performing an operation that results in a scaled estimation of the correlation between the measured relative wind direction change and the change in the performance parameter, wherein the determining the correlation value between measured relative wind direction change and the performance change comprises multiplying the measured relative wind direction change and the performance change; 
 measuring further plural samples of the relative wind direction; and 
 correcting the further measured relative wind directions based on the correlation value, such that the correlation value approaches closer to zero; 
 wherein an effective wind speed is estimated using a turbine model, taking into account at least one of actual power produced, actual rotor speed, and actual pitch angle and wherein the performance parameter comprises the effective wind speed. 
 
     
     
       2. The method according to  claim 1 , wherein the method is continuously, iteratively performed, during normal operation. 
     
     
       3. The method according to  claim 1 , wherein the method is performed irrespective whether at least one of the wind direction, a wind speed and a yaw position changes or not. 
     
     
       4. The method according to  claim 1 , wherein the performance parameter further comprises at least one of the following:
 a power, wherein the power is an active power, produced by the wind turbine, applied in low and medium wind ranges; 
 a pitch angle, applied at high wind speed; 
 an increase in rotor speed; 
 a quantity being or being related to a load of at least one wind turbine component. 
 
     
     
       5. The method according to  claim 1 , wherein the deriving the measured wind direction change comprises:
 passing the plural measured samples of the relative wind direction through a low time constant low pass filter and a high time constant low pass filter and forming a difference of outputs of the two low pass filters. 
 
     
     
       6. The method according to  claim 1 , wherein the deriving the performance change comprises:
 passing the plural measured samples of the performance parameter through a low time constant low pass filter and a high time constant low pass filter and forming a difference of outputs of two low pass filters. 
 
     
     
       7. The method according to  claim 1 , wherein the correcting the measured relative wind direction based on the correlation value comprises:
 modifying the measured relative wind direction based on the correlation value such that a correlation between future modified measured relative wind direction and the future performance parameter decreases. 
 
     
     
       8. The method according to  claim 1 , wherein the correcting the measured relative wind direction based on the correlation value comprises:
 subtracting a value proportional to the correlation value from the measured relative wind direction. 
 
     
     
       9. The method according to  claim 8 , wherein
 a proportionality factor is selected to avoid overshooting. 
 
     
     
       10. The method according to  claim 1 , further comprising:
 storing the determined correlation value, in dependence or association of at least one operational and environmental parameter, wherein the at least one operational and environmental parameter is a wind speed. 
 
     
     
       11. The method according to  claim 10 , further comprising:
 determining at least one operational and/or environmental parameter, wherein the at least one operational and/or environmental parameter is the wind speed; and 
 subtracting a value proportional to the correlation value associated to the wind speed, to obtain the corrected measured relative wind direction. 
 
     
     
       12. The method according to  claim 1 , wherein the determining the correlation value between the measured relative wind direction change and the performance change includes determining a degree of mutual dependence of the measured relative wind direction change and the performance change. 
     
     
       13. The method according to  claim 1 , wherein the correlation value is positive if:
 the measured relative wind direction change is positive and also the performance change is positive; or 
 the measured relative wind direction change is negative and the performance change is negative. 
 
     
     
       14. The method according to  claim 1 , wherein the correlation value is negative if:
 the measured relative wind direction change is negative and also the performance change is positive; or 
 the measured relative wind direction change is positive and the performance change is negative. 
 
     
     
       15. The method according to  claim 1 , wherein the correlation value is a mean correlation value averaged over all reasonable wind speeds, the method further comprising correcting the further measured relative wind directions based on a single averaged correlation value. 
     
     
       16. A method for performing a wind direction measurement for a wind turbine, the method comprising:
 measuring plural samples of a relative wind direction representing a difference angle between a real wind direction and an orientation of a measurement equipment, to obtain plural measured relative wind directions, wherein the orientation is a direction orthogonal to a rotor blade plane; 
 deriving a measured relative wind direction change based on the measured relative wind directions; 
 measuring plural samples of a performance parameter indicating a performance of the wind turbine; 
 deriving a performance change based on the plural samples of the performance parameter; 
 determining a correlation value between the measured relative wind direction change and the performance change, wherein the correlation value is a mean correlation value averaged over all reasonable wind speeds; 
 measuring further plural samples of the relative wind direction; and 
 correcting the measured relative wind directions based on a single averaged correlation value, such that the correlation value approaches closer to zero; 
 wherein an effective wind speed is estimated using a turbine model, taking into account at least one of actual power produced, actual rotor speed, and actual pitch angle and wherein the performance parameter comprises the effective wind speed. 
 
     
     
       17. A method for performing a wind direction measurement for a wind turbine, the method comprising:
 measuring plural samples of a relative wind direction representing a difference angle between a real wind direction and an orientation of a measurement equipment, to obtain plural measured relative wind directions, wherein the orientation is a direction orthogonal to a rotor blade plane; 
 deriving a measured relative wind direction change based on the measured relative wind directions; 
 measuring plural samples of a performance parameter indicating a performance of the wind turbine; 
 deriving a performance change based on the plural samples of the performance parameter; 
 determining a correlation value between the measured relative wind direction change and the performance change including performing an operation that results in a scaled estimation of the correlation between the measured relative wind direction change and the change in the performance parameter, wherein the correlation value is a mean correlation value averaged over all reasonable wind speeds; 
 measuring further plural samples of the relative wind direction; and 
 correcting the further measured relative wind directions based on the correlation value, such that the correlation value approaches closer to zero; 
 correcting the further measured relative wind directions based on a single averaged correlation value; 
 wherein an effective wind speed is estimated using a turbine model, taking into account at least one of actual power produced, actual rotor speed, and actual pitch angle and wherein the performance parameter comprises the effective wind speed.